Cathelicidin
hCAP18, the precursor the body cuts to release LL-37, its only cathelicidin peptide
Cathelicidin is the family name; in humans there is one, hCAP18, made by many cell types, with neutrophil precursors the main source in blood. Cutting it releases LL-37, the antimicrobial peptide. Vitamin D switches its gene on. Its human studies measure it in blood and urine; nobody has been given cathelicidin as a treatment.
What is it?
Cathelicidins are a family of antimicrobial proteins found across mammals. Humans make one, from the CAMP gene: a precursor called hCAP18 that is cut outside the cell to release LL-37. LL-37 kills bacteria, fungi and some viruses, attracts immune cells and promotes wound healing and new blood vessels, which is why it gets its own entry here.
Vitamin D is the best-known switch. In human monocyte cells, a physiological concentration raised CAMP gene activity about 170-fold and hCAP18/LL-37 protein three- to fourfold. The same work found LL-37 at that concentration was toxic to bone-forming cells, a reminder that antimicrobial peptides are not harmless to their host.
In people, cathelicidin is measured rather than given. Serum hCAP18 tracks neutrophil production: children with acute leukaemia, aplastic anaemia or myelodysplasia had low levels and children with chronic myeloid leukaemia high ones. In 80 adults, serum levels shifted after a fatty meal and correlated with LDL cholesterol.
Its protective role is clearest in the urinary tract. Bladder cells release LL-37 into urine on contact with bacteria, mice lacking their cathelicidin got worse infections, and E. coli strains more resistant to LL-37 caused more severe infections in patients.
At a Glance
Every value in this table is printed from the Grey Peptides dataset, the same record the compound explorer and comparison tool read, so the three can never disagree.
Published Research
These are the studies that describe cathelicidin, read from their PubMed abstracts: two measurement studies in people, a urinary-tract study, a vitamin D cell study and a review of LL-37.
A marker of neutrophil production
Serum hCAP18 was measured in healthy children and children with blood cancers. Diseases that impair myelopoiesis — acute leukaemia, aplastic anaemia, myelodysplasia — gave low levels; chronic myeloid leukaemia gave high ones; solid tumours were normal.
After a fatty meal
In 80 volunteers, serum cathelicidin averaged 55.8 ng/mL, changed over six hours after oral lipid, correlated positively with LDL and negatively with HDL and adiponectin, and was higher in men than in women.
Guarding the urinary tract
Bacterial contact made urinary epithelial cells release cathelicidin; in people LL-37/hCAP18 appeared in urine. Mice lacking it had more infection, and E. coli strains resistant to LL-37 caused more severe urinary infections.
Vitamin D turns it on
In human monocyte cells, 50 nM vitamin D raised CAMP mRNA about 170-fold and hCAP18/LL-37 protein three- to fourfold; LL-37 at the resulting concentration reduced the viability of bone-forming cells.
What LL-37 does
A review of LL-37's antibacterial, antifungal and antiviral activity, its effects on immune cells, wound healing and blood vessel growth, and its emerging role in cancer.
Side Effects & Contraindications
Reported Side Effects
Nothing to report from treatment; none has been tested.
Contraindications & Cautions
A natural protein, studied as a marker.
Legal Status
No cathelicidin product is approved anywhere.
Frequently Asked Questions
?What is cathelicidin?
In humans, hCAP18, a precursor protein the body cuts to release LL-37, an antimicrobial peptide.
?How is it different from LL-37?
LL-37 is the active peptide; cathelicidin is the larger protein it comes from.
?Does vitamin D raise it?
In cells, vitamin D raised its gene activity about 170-fold. Whether supplements change infection risk is a separate question.
?Can I take it?
No product exists, and it has never been tested as a treatment.
References
- [pubmed] Jackmann N, et al. "The human cathelicidin hCAP-18 in serum of children with haemato-oncological diseases." Br J Haematol, 2022;198(6):1023-1031. PMID: 35849644.
- [pubmed] Höpfinger A, et al. "Circulating Levels of Cathelicidin Antimicrobial Peptide (CAMP) Are Affected by Oral Lipid Ingestion." Nutrients, 2023;15(13). PMID: 37447348.
- [pubmed] Chromek M, et al. "The antimicrobial peptide cathelicidin protects the urinary tract against invasive bacterial infection." Nat Med, 2006;12(6):636-41. PMID: 16751768.
- [pubmed] Aidoukovitch A, et al. "Vitamin D triggers hCAP18/LL-37 production: Implications for LL-37-induced human osteoblast cytotoxicity." Biochem Biophys Res Commun, 2024;712-713:149962. PMID: 38642493.
- [pubmed] Vandamme D, et al. "A comprehensive summary of LL-37, the factotum human cathelicidin peptide." Cell Immunol, 2012;280(1):22-35. PMID: 23246832.
- [pubmed] Liu PT, et al. "Toll-like receptor triggering of a vitamin D-mediated human antimicrobial response." Science, 2006;311(5768):1770-3. PMID: 16497887.
- [other] US FDA, Drugs@FDA (openFDA): no application for cathelicidin or hCAP18. Read September 30, 2026.
Sources & Citations
Studies were read from PubMed; regulatory status comes from openFDA, read September 30, 2026.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Consult a licensed healthcare provider before making health decisions.